A monitoring system is widely adopted in stores such as convenience stores, in which cameras are set up in each store to capture images of an interior of the store so that persons in the store can be monitored by the images captured by the cameras. If an arrangement is made to enable grasping the state of movement of persons in the store by use of the images captured by the cameras, it becomes possible to attempt to increase the sales and profit of the store by contemplating an improvement of the way of displaying items in the store, etc.
As a technology relating to such analysis of the state of movement of customers in the store, a technology is conventionally known which sets a detection line on the images obtained by a camera that captures images of a monitored area, and counts the persons moving across the detection line (see Patent Document 1). In this technology, to address a problem that an erroneous counting may occur when the images are obtained by image-capturing the monitored area at an oblique angle with a camera having a predetermined angle of view, such as a box camera, the counting is performed taking into account the direction of movement of the persons, to thereby improve the measurement accuracy.